Manifold for connecting circuits of a central heating system

ABSTRACT

A manifold connects three boiler circuits and a heat exchanger circuit and an indirect cylinder heated exchanger circuit of a central heating system together. The manifold comprises a container which defines a hollow interior region which is divided by a horizontally extending partition plate into an upper flow water region and a lower return water region. First ports are provided for connecting flow pipes of the circuits into the flow water region of the manifold and second ports are provided for connecting the return pipes of the circuits into the return water region of the manifold. A communicating opening and apertures in the partition plate communicate the flow and return water regions. The partition plate stratifies the water within the hollow interior region so that the hottest flow water is above while the cooler return water is below the partition plate. The manifold forms neutral pressure point in the system so that the circuit can operate independently of each other, while at the same the circuit operate in association with the boiler circuits.

The present invention relates to a manifold for connecting two or morecircuits of a liquid, heat transfer medium central heating system,typically, a central heating system in which the liquid heat transfermedium is water, for example, a hot water central heating system, andthe invention also relates to a central heating system.

In many cases, it is desirable to connect two or more circuits of acentral heating system together. However, when connecting such circuits,it is desirable that at least some of the circuits should be capable offunctioning independently of some of the other circuits, and inassociation with those and others of the circuits. For example, it isdesirable that if two or more boilers are connected into a centralheating system that the boiler circuits should be capable of beingfunctioning independently of each other. In other words, when only oneof the boilers is operating, the heat transfer medium should notcirculate through the idle boiler or boilers. Otherwise, the idleboilers act as heatsinks. Additionally, should the central heatingsystem comprise two or more circuits, each of which comprises aplurality of heat exchangers, for example, central heating radiators, oran indirect hot water tank, it is desirable that the two or more heatexchanger circuits should be capable of functioning independently ofeach other, but in association with one or more boiler circuits of thecentral heating system, so that heat transfer medium only circulates inthose heat exchange circuits which are to be operated, and only throughthe boiler or boilers of the boiler circuits in which the boiler orboilers are operating.

In general, the only known satisfactory method of operating a centralheating system with two or more heat exchanger circuits and one or moreboiler circuits is to interconnect the respective circuits through aseries of valves, typically solenoid operated valves. The solenoidvalves are appropriately operated for connecting the heat exchangercircuits which are to operate to the corresponding boiler or boilercircuits for providing heated heat transfer medium to the appropriateheat exchanger circuit or circuits. Such interconnecting arrangementswith solenoid valves, while they achieve the objective, requirerelatively complex control circuitry, and are relatively complex andexpensive to install. The solenoid valves are relatively expensive, asis the control circuitry.

Attempts to interconnect two or more circuits of a central heatingsystem have been made by the provision of a manifold, however, to dateall such attempts have been relatively unsuccessful. Known manifoldstend to be relatively inefficient. In such known manifolds colder returnheat transfer medium from a heat exchanger circuit tends to berecirculated through the flow line of that or another heat exchangercircuit. It has been found that at best the colder heat transfer mediumfrom a heat exchanger circuit mixes with the warmer flow heat transfermedium received from a boiler circuit in the manifold, and a mixture ofthe flow and return heat transfer medium is circulated through the flowline of the heat exchanger circuits. This, is inefficient and isundesirable.

There is therefore a need for a manifold for connecting two or morecircuits of a liquid, heat transfer medium central heating systemtogether which overcomes the problems of known manifolds.

The present invention is directed towards providing such a manifold, anda central heating system incorporating the manifold.

According to the invention there is provided a manifold for connectingat least two circuits of a liquid, heat transfer medium central heatingsystem in which the circuits each comprise a flow line and a returnline, so that at least some of the circuits can function independentlyof each other and at least some of the circuits can function inassociation with each other, the manifold comprising a containerdefining an enclosed hollow interior region for the heat transfermedium, and a plurality of pairs of first and second ports to the hollowinterior region for connecting the respective circuits to the hollowinterior region, the first ports being provided for connecting the flowlines of the respective circuits into the hollow interior region, andthe second ports being provided for connecting the return lines of therespective circuits into the hollow interior region, characterised inthat a partitioning means extends transversely of the hollow interiorregion for dividing the hollow interior region into a flow heat transfermedium region and a return heat transfer medium region, the respectiveregions communicating with each other through a communicating means inthe partitioning means, the first ports communicating with the flow heattransfer medium region, and the second ports communicating with thereturn heat transfer medium region.

The advantages of the invention are many. The manifold according to theinvention is particularly efficient in use, is easy to install, and alsorelatively inexpensive to provide and install. It can be installedwithout the need for any complex control circuitry. By virtue of thefact that a partitioning means divides the hollow interior region into aflow heat transfer medium and a return heat transfer medium region, andthe first and second ports communicate with the respective regions,there is little mixing if any of flow and return heat transfer medium inthe manifold. Thus, heat exchanger circuits receive flow heat transfermedium at a temperature substantially at that at which it is receivedinto the manifold from a boiler circuit, without being diluted by thecooler return heat transfer medium, and likewise, the cooler return heattransfer medium from the heat exchanger circuits is returned directly tothe boiler or boilers which are operating without being diluted withhotter flow heat transfer medium. The communicating means forcommunicating the flow and return heat transfer medium regions throughthe partitioning means causes the manifold to create a neutral pressurepoint in the central heating system which ensures that the respectivecircuits which are connected to the manifold operate independently ofeach other, while at the same time permitting heat exchanger circuits tooperate in association with boiler circuits.

Preferably, the partitioning means comprises a partition plate.

By providing the partitioning means as a partition plate a particularlyconvenient and advantageous form of the manifold is provided.

In one aspect of the invention the partitioning plate extendssubstantially completely across the hollow interior region.

Preferably, the communicating means is provided by at least onecommunicating aperture which is formed in and extends through thepartitioning means for communicating the respective regions with eachother.

Advantageously, the communicating means is provided by a communicatingopening which is formed between the partitioning means and a wall of thecontainer.

The provision of the communicating means in the form of an aperturethrough the partitioning means facilitates the formation of the neutralpressure point in the hollow interior region, while at the same time,minimising mixing between the flow and return heat transfer medium. Thiseffect is also achieved by forming the communicating means between thepartitioning means and a wall of the manifold.

Preferably, the first and second ports are located in pairs of adjacentfirst and second ports.

The provision of the first and second ports in pairs facilitates ease ofinstallation of manifold.

In one embodiment of the invention at least one of the first ports islocated in a wall of the container which forms part of the return heattransfer medium region, and a first connecting pipe extends from each ofsaid first ports through the return heat transfer medium region andthrough the partitioning means for communicating the respective saidfirst ports with the flow heat transfer medium region.

In another embodiment of the invention at least one of the second portsis located in a wall of the container which forms part of the flow heattransfer medium region, and a second connecting pipe extends from eachof said second ports through the flow heat transfer medium region andthrough the partitioning means for communicating the respective saidsecond ports with the return heat transfer medium region.

Preferably, the partitioning means lies in a plane which extendshorizontally, the flow heat transfer medium region being located abovethe return heat transfer medium region for stratifying the heat transfermedium in the hollow interior region so that the hotter heat transfermedium is in the flow heat transfer medium region.

In one embodiment of the invention the container is an elongatedcontainer.

In another embodiment of the invention the container is adapted formounting with its longitudinally extending axis extending substantiallyhorizontally.

In an alternative embodiment of the invention the container is adaptedfor mounting with its longitudinally extending axis extendingsubstantially vertically.

A particularly important advantage of the invention is achieved byarranging the partitioning means in the manifold so that when installedthe partitioning means lies in a horizontal plane with the flow heattransfer medium region above the return heat transfer medium region, inthat stratification of the heat transfer medium is facilitated with thehotter flow heat transfer medium above the cooler return heat transfermedium, thereby further minimising mixing between the flow and returnheat transfer medium.

In on embodiment of the invention each first port for delivering heattransfer medium into the flow heat transfer medium region is providedwith a means for directing the heat transfer medium into the flow heattransfer medium region upwardly into the said region.

In another embodiment of the invention each first port through whichheat transfer medium is drawn from the flow heat transfer medium regionis provided with a means for directing the heat transfer medium beingdrawn from the flow heat transfer medium region downwardly towards thesaid first port.

In a further embodiment of the invention each second port for deliveringheat transfer medium into the return heat transfer medium region isprovided with a means for directing the heat transfer medium beingdelivered into the return heat transfer medium region downwardly intothe said region.

In a still further embodiment of the invention each second port throughwhich heat transfer medium is drawn from the return heat transfer mediumregion is provided with a means for directing the heat transfer mediumbeing drawn from the return heat transfer medium region upwardly towardsthe said second port.

In one aspect of the invention at least two pairs of first and secondports are provided for connecting two circuits each having at least oneheat exchanger for transferring heat from the heat transfer medium inthe respective circuits.

In another aspect of the invention at least two pairs of first andsecond ports are provided for connecting two circuits each having atleast one heat source for heating the heat transfer medium.

In a preferred embodiment of the invention the container comprises a topwall and a bottom wall, the first and second ports being located in thetop and bottom walls, the second ports which are located in the topwall, communicating with the return heat transfer medium region throughthe second connecting pipes, and the first ports which are located inthe bottom wall communicating with the flow heat transfer medium regionthrough the first connecting pipes. Preferably, the container comprisesa pair of spaced apart end walls joining the top and bottom walls,respective first and second ports being located in end walls.

Additionally the invention provides a central heating system comprisingat least two circuits within which a liquid heat transfer medium iscirculated, the circuits each having a flow line and a return line, andthe manifold according to the invention connecting the at least twocircuits together, the flow lines of the respective circuits beingconnected to the first ports of the manifold, and the return lines ofthe respective circuits being connected to the second ports.

In one embodiment of the invention at least two circuits of the centralheating system comprise at least one heat exchanger each fortransferring heat from the heat transfer medium in the respectivecircuits.

In another embodiment of the invention at least two of the circuits ofthe central heating system comprise at least one heat source each forheating the heat transfer medium.

The invention will be more clearly understood from the followingdescription of some preferred embodiments thereof which are given by wayof example only, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a manifold according to the inventionfor connecting together a plurality of circuits of a central heatingsystem, also according to the invention,

FIG. 2 is a partly cut away perspective view of the manifold of FIG. 1,

FIG. 3 is a sectional side elevational view of the manifold of FIG. 1,

FIG. 4 is a sectional plan view of the manifold of FIG. 1 on the lineIV--IV of FIG. 3,

FIG. 5 is a sectional end elevational view on the line V--V of FIG. 4,

FIG. 6 is a circuit diagram of a central heating system according to theinvention incorporating the manifold of FIG. 1,

FIG. 7 is a circuit diagram of a central heating system according toanother embodiment of the invention incorporating the manifold of FIG.1,

FIG. 8 is a view similar to FIG. 3 of a manifold according to anotherembodiment of the invention,

FIG. 9 is a cross-sectional plan view similar to FIG. 4 of the manifoldof FIG. 8 on the line IX--IX of FIG. 8,

FIG. 10 is a cross-sectional view similar to FIG. 5 of the manifold ofFIG. 8 on the line X--X of FIG. 8,

FIG. 11 is a circuit diagram of a central heating system according toanother embodiment of the invention incorporating the manifolds of FIGS.1 and 8,

FIG. 12 is a cross-sectional side elevational view of a manifoldaccording to a further embodiment of the invention,

FIG. 13 is a cross-sectional plan view of the manifold of FIG. 12 on theline XIII--XIII of FIG. 12,

FIG. 14 is an elevational view of a part of a circuit of a centralheating system incorporating the device of FIGS. 12 and 13, and

FIG. 15 is a plan view of the part of the circuit of FIG. 14.

Referring to the drawings and initially to FIGS. 1 to 6 there isillustrated a manifold according to the invention indicated generally bythe reference numeral 1 for connecting a plurality of circuits of acentral heating system together so that each of the circuits canfunction independently of the other circuits and some of the circuitscan function in association with others of the circuits. In FIG. 6 themanifold 1 is illustrated in a sealed hot water central heating systemindicated generally by the reference numeral 2 also according to theinvention which comprises three boiler circuits 3, 4 and 5, and two heatexchanger circuits, namely, a radiator heat exchanger circuit 6, anindirect hot water heat exchanger circuit 7. The boiler circuits 3, 4and 5 each comprise a boiler 8, 9 and 10, respectively. The radiatorheat exchanger circuit 6 comprises three heat exchangers, namely, threeradiators 11, and needless to say it will be appreciated the heatexchanger circuit 6 may comprise many more radiators 11, and indeed,other heat exchangers, for example, fan heaters and the like. Theindirect water heat exchanger circuits 7 comprises an indirect hot watertank 12 for providing domestic hot water. Flow and return pipes 15 and16, respectively, of the respective circuits 3 to 7 are connectedtogether by the manifold 1 as will be described below. Pumps 17 in therespective circuits 3 to 7, inclusive, circulate heat transfer medium,in this case water in the respective circuits 3 to 7 through themanifold 1 as will be described below.

The manifold 1 comprises an elongated container 20 of suitable platemetal material, typically, steel plate material which comprises a topwall 21, a bottom wall 22, side walls 23 and end walls 24, all of whichin combination define an enclosed hollow interior region 25 forcontaining heat transfer medium, which in this case, is water. Apartitioning means, namely, a partition plate 28 also of metal platematerial, typically, steel plate material extends transversely acrossthe hollow interior region 25, and divides the hollow interior region 25into an upper flow water region 29 and a lower return water region 30.The partition plate is welded to the side walls 23. In use, the manifold1 is mounted so that its longitudinal axis extends horizontally, and thepartition plate 28 lies in a horizontal plane so that the flow waterregion 29 which contains hotter water is above the return water region30. This facilitates stratification of the water in the hollow interiorregion 25 so that hotter flow water is above the cooler return water.

A communicating means for communicating the flow and return waterregions 29 and 30, respectively, with each other so that the hollowinterior region 25 of the manifold forms a neutral pressure point of thecentral heating system 2 is provided by a pair of communicating openings32 which are formed at respective ends of the partition plate 28 betweenend edges 33 of the partition plate 28 and the end walls 24 of thecontainer 20.

A plurality of first and second ports 35 and 36, respectively, arelocated in the top and bottom walls 21 and 22 and in the end walls 24for connecting the flow and return pipes 15 and 16 of the circuits 3 to7, inclusive, with the hollow interior region 25. The first ports 35 allterminate in and communicate with the flow water region 29, and connectthe flow pipes 15 into the flow water region 29. The second ports 36 allterminate in and communicate with the return water region 30 and connectthe return pipes 16 into the return water region 30. The first andsecond ports 35 and 36 are arranged in pairs, one pair being located onthe top wall 21, two pairs being located on the bottom wall 22, and onepair being located on each of the end walls 24. First connecting pipes37 extend from the two first ports 35 which are located in the bottomwall 22 and extend through the return water region 30 and throughcommunicating apertures 38 in the partition plate 28, and terminate inthe flow water region 29. A second connecting pipe 39 extends from thesecond port 36 which is located in the top wall 21 and extends throughthe flow water region 29 and through a communicating aperture 38 in thepartition plate 28 to terminate in the return water region 30. Clearanceis provided in the communicating apertures 38 around the first andsecond connecting pipes 37 and 39, respectively, and the partition plate28, so that the communicating apertures also act as the communicatingmeans between the flow and return water regions 29 and 30, respectively.

A third port 40 located in the bottom wall 22 communicates with thereturn water region 30 for connecting an expansion vessel 41 of thesystem 2 into the manifold 1. In the case of a gravity fed centralheating system, the header tank would normally be connected to the thirdport 40.

The manifold 1 forms a neutral pressure point in the central heatingsystem 2 where there is no pressure differential for urging waterthrough any of the circuits. Accordingly, only those circuits, the pumps17 of which are operating circulate water in their respective circuitsand through the manifold 1. Thus, if only one of the boilers 8, 9 and 10is operating, and its associated pump 17 is circulating water throughthat boiler and the manifold 1, provided the associated pumps 17 of theremaining two non-operating boilers are not operating no water passesthrough the non-operating boilers, and thus, there is no danger of aboiler which is not operating acting as a heatsink. That is of courseprovided that the boiler circuits 3, 4 and 5 of the boilers areincapable of acting under gravity. Likewise, provided the heat exchangercircuit 6 and the indirect heat exchanger circuit 7 are incapable ofacting under gravity, no water will circulate through these circuitsunless their associated pumps 17 are operating. Accordingly, if only oneboiler is operating, for example, the boiler 8, and only the pump 17 ofthe boiler circuit 3 is operating, and furthermore, none of the pumps 17of the two circuits 6 and 7 are operating, hot water is merelycirculated through the boiler 8 and the manifold 1. The hot water fromthe boiler 8 enters the flow water chamber 29 through the correspondingfirst port 35 from the flow line 15 of the circuit 3, and is returned tothe boiler 16 from the return water chamber 30 through the correspondingsecond port 36 into the return line 16. On the pump 17 of the heatexchanger circuit 6 being operated hot water is circulated through theheat exchanger circuit 6. The pump 17 of the heat exchanger circuit 6draws water from the flow water region 29 through the correspondingfirst port 35 which is delivered into the flow line 15. Return waterfrom the heat exchanger circuit 6 is returned through the return line 16and the corresponding second port 36 into the return water region 30.Thus, the flow water drawn from the manifold 1 into the heat exchangercircuit 6 is at substantially the same temperature as the flow waterreceived into the manifold 1 from the boiler 8. Similarly, the returnwater from the heat exchanger circuit 6 is substantially the sametemperature as the return water being returned to the boiler 8. Thepartition plate 28 separates the hotter flow water from the colderreturn water, while the communicating openings 32 and the communicatingapertures 38 permit flow of water between the flow and return waterregions 29 and 30. For so long as the pumps 17 of the boiler circuits 4and 5 and the indirect heat exchanger circuit 7 remain non-operatingthere is no water circulating in any of the circuits 4, 5 and 7.However, as soon as any of the pumps 17 of the circuits 4, 5 and 7 areoperated, circulation of water takes place in the corresponding circuitsin a manner already discussed. Accordingly, the boiler circuits 3, 4 and5 may be operated independently of each other and independently of thecircuits 6 and 7 but also in association with the circuit 6 and 7.Additionally, the circuit 6 and 7 may be operated independently of eachother and independently of the boiler circuits 3, 4 and 5, but also inassociation with the boiler circuits 3, 4 and 5.

Referring now to FIG. 7 there is illustrated a central heating systemaccording to another embodiment of the invention indicated generally bythe reference numeral 45. The central heating system 45 is substantiallysimilar to the central heating system 2 of FIG. 6, and similarcomponents are identified by the same reference numerals. In thisembodiment of the invention the central heating system 45 comprises twoheat exchanger circuits 6, only one of which is illustrated in full, anindirect hot water heat exchanger circuit 7 and two boiler circuits 3and 4, all of which are connected together by the manifold 1. However,in this embodiment of the invention the manifold 1 is inverted so thatthe bottom wall 22 forms the top wall of the container 20 and viceversa. Thus, the region which in the embodiment of the inventiondescribed with reference to FIGS. 1 to 6 forms the flow water region 29now forms the return water region 30 and vice versa. However, otherwise,the operation of the manifold 1 and of the central heating system 45 issimilar to that already described.

Referring now to FIGS. 8 to 10 there is illustrated a manifold accordingto a further embodiment of the invention indicated generally by thereference numeral 50. The manifold 50 is substantially similar to themanifold 1 and similar components are identified by the same referencenumerals. The main difference between the device 50 and the device 1 isthat there are more first and second ports 35 and 36 entering throughthe bottom wall 22 and none entering through the top wall 21. A ventport 51 is provided in the top wall 21 for connecting to an automaticvent for venting the manifold 50. Additionally, in this embodiment ofthe invention the communicating means is formed by a communicatingopening 32 which extends around two sides and one end of the partitionplate 28 and is formed between side edges 52 of the partition plate 28and corresponding side walls 23 of the container 20, and an end edge 53of the partition plate 28 and one of the end walls 24 of the container20. The partition plate 28 is welded to the other end wall 24.Otherwise, the manifold 50 and the connection of the manifold 50 into acentral heating system for connecting a plurality of circuits togetheris identical to that already described.

Referring now to FIG. 11 there is illustrated a central heating system55 according to another embodiment of the invention which issubstantially similar to the central heating system 2 of FIG. 6 andsimilar components are identified by the same reference numerals. Themain difference between this central heating system 55 and the centralheating system 2 is that two manifolds, namely, a manifold 1 and amanifold 50 are used for connecting the circuits and the central heatingsystem together. The manifold 1 connects two boiler circuits, namely, aboiler circuit 3 and a boiler circuit 4, and two heat exchanger circuits6 together. A flow and return pipe 56 and 57, respectively connect themanifold 50 to the manifold 1. A circulating pump 58 in the return pipe57 circulates water between the two manifolds 1 and 50. The flow pipe 56is connected to respective first ports 35 of the manifolds 1 and 50, andthe return pipe 57 is connected to respective second ports 36 of themanifolds 1 and 50. Three further heat exchanger circuits 6 withassociated pumps 17 are connected to respective first and second ports35 and 36 of the manifold 50 and an indirect heat exchanger circuit 7with an associated pump 17 is connected to respective first and secondports 35 and 36 of the manifold 50. A further pair of first and secondports 35 and 36 in an end wall 24 of the manifold 50 are blanked off,but may be used for connecting either another circuit 6 or 7 or a boilercircuit as desired.

The pump 58 is interlocked with the pumps 17 of the circuits 6 and 7which are connected into the manifold 50 so that on a demand for hotwater from any of the circuits 6 and 7 which are connected into themanifold 50 the pump 58 is operated for circulating water between themanifolds 1 and 50. Alternatively, the pump 58 may be continuouslyoperated while any of the circuits of the system 55 are in operation.

Referring now to FIGS. 12 and 13 there is illustrated a manifoldindicated generally by the reference numeral 60 according to a stillfurther embodiment of the invention. In this embodiment of the inventionthe manifold 60 comprises a container 61 of steel plate material havingtop and bottom walls 61 and 62 which are joined by four side walls 63.The top and bottom walls 61 and 62 and side walls 63 define a hollowinterior region 64 which is divided by a partitioning means, namely, apartition plate 65 of steel plate material which divides the hollowinterior region 64 into an upper flow water region 66 and a lower returnwater region 67. A communicating means, namely a communicating aperture68 through the partition plate 65 communicates the flow and return waterregions 66 and 67. This manifold 60 is substantially similar to themanifold 1 with the exception that the manifold 60 is essentiallymounted with its longitudinal axis extending vertically. However, as canbe seen in FIG. 12 the partition plate 65 extends in a horizontal planefor stratifying the flow and return water in similar fashion as thepartition plate 28 stratifies the flow and return water in themanifold 1. A plurality of first ports 70 extend into the flow waterregion 66 for connecting flow pipes of respective circuits which areconnected to the manifold 60 into the flow water region 66. Second ports73 and 74 extending into the return water region 67 connect return pipesof circuits into the return water region 67. In this embodiment of theinvention a means for directing the flow water being delivered into theflow water region 66 from the first ports 70 upwardly into the flowwater region 66 comprises a plurality of slots 78 in the upper half ofthe first ports 70. The slots 78 deliver flow water into the first ports70 downwardly from the flow water region 66 into circuits which compriseheat exchangers. The advantage of providing the water directing slots 78in this fashion is that it further facilitates in stratifying the waterin the hollow interior region 64 so that the hottest water is deliveredinto and drawn off from the top of the flow water region 66 by therespective first ports of the flow lines of the circuits. In similarfashion, a means for directing return water downwardly into the returnwater region 67 from the second ports 73, and for receiving return waterupwardly into the second ports 73 comprises slots 79 similar to theslots 78 but located in the lower half of the second port 73. Theadvantage of this is that it ensures that the coldest water is returnedto and/or drawn from the lowest part of the return water region 67.

FIGS. 13 and 14 illustrate four boiler circuits 80 to 83, respectively,connected in a central heating system 84 by the manifold 60. Two heatexchanger circuits 85 and 86 are also connected into the central heatingsystem 84 by the manifold 60. Only the flow and return pipes 15 and 16of the heat exchanger circuits 85 and 86 are illustrated.

A third port 87 to the flow water region 66 is provided for receiving anautomatic venting valve 88 for venting the system. One of the advantagesof providing a vent in the manifold 60, and indeed, in the manifold 50is that by virtue of the fact that the manifolds essentially form aneutral pressure point in the central heating system, air tends toexpand out of the water in the manifolds, and thus, can be readilyeasily vented from the system.

I claim:
 1. A manifold (1) for connecting at least two circuits (3 to 7)of a liquid, heat transfer medium central heating system (2) in whichthe circuits (3 to 7) each comprise a flow line (15) and a return line(16), so that at least some of the circuits (3 to 7) can functionindependently of each other and at least some of the circuits (3 to 7)can function in association with each other, the manifold (1) comprisinga container (20) defining an enclosed hollow interior region (25) forthe heat transfer medium, and a plurality of pairs of first and secondports (35, 36, 70, 73) to the hollow interior region (25) for connectingthe respective circuits (3 to 7) into the hollow interior region (25),the first ports (35, 70) being provided for connecting the flow lines(15) of the respective circuits (3 to 7) to the hollow interior region(25), and the second ports (36, 73) being provided for connecting thereturn lines (16) of the respective circuits (3 to 7) into the hollowinterior region (25), characterised in that a partitioning means (28)extends transversely of the hollow interior region (25) for dividing thehollow interior region (25) into a flow heat transfer medium region (29)and a return heat transfer medium region (30), the respective regions(29, 30) communicating with each other through a communicating means(32, 38) in the partitioning means (28), the first ports (35, 70)communicating with the flow heat transfer medium region (29), and thesecond ports (36, 73) communicating with the return heat transfer mediumregion (30) and at least one of the first ports (35, 70) is located in awall (22) of the container (20) which forms part of the return heattransfer medium region (30), and a first connecting pipe (37) extendsfrom each of said first ports (35, 70) through the return heat transfermedium region (30) and through the partitioning means (28) forcommunicating the respective said first ports (35, 70) with the flowheat transfer medium region (29).
 2. A manifold (1) as claimed in claim1 characterised in that the partitioning means (28) comprises apartition plate (28).
 3. A manifold (1) as claimed in claim 2characterised in that the partition plate (28) extends substantiallycompletely across the hollow interior region (25).
 4. A manifold (1) asclaimed in claim 1 characterised in that the communicating means (32,38)is provided by at least one communicating aperture (38) which is formedin and extends through the partitioning means (28) for communicating therespective regions (29,30) with each other.
 5. A manifold (1) as claimedin claim 1 characterised the communicating means (32,38) is provided bya communicating opening (32) which is formed between the partitioningmeans (28) and a wall of the container (20).
 6. A manifold (1) asclaimed in claim 1 characterised in that the first and second ports(35,36) are located in pairs of adjacent first and second ports (35,36).7. A manifold (1) as claimed in claim 1 characterised in that at leastone of the second ports (36, 73) is located in a wall (21) of thecontainer (20) which forms part of the flow heat transfer medium region(29), and a second connecting pipe (39) extends from each of said secondports (36, 73) through the flow heat transfer medium region (29) andthrough the partitioning means (28) for communicating the respectivesaid second ports (36, 73) with the return heat transfer medium region(30).
 8. A manifold (1) as claimed in claim 1 characterised in that thepartitioning means (28) lies in a plane which extends horizontally, theflow heat transfer medium region (29) being located above the returnheat transfer medium region (30) for stratifying the heat transfermedium in the hollow interior region (25) so that the hotter heattransfer medium is in the flow heat transfer medium region (29).
 9. Amanifold (1) as claimed in claim 1 characterised in that the container(20) is an elongated container (20).
 10. A manifold (1) as claimed inclaim 9 characterised in that the container (20) is adapted for mountingwith its longitudinally extending axis extending substantiallyhorizontally.
 11. A manifold (1) as claimed in claim 1 characterised inthat the container (20) is adapted for mounting with its longitudinallyextending axis extending substantially vertically.
 12. A manifold (1) asclaimed in claim 1 characterised in that each first port (35, 70) fordelivering heat transfer medium into the flow heat transfer mediumregion (66) is provided with a means (78) for directing the heattransfer medium into the flow heat transfer medium region (66) upwardlyinto the said region (66).
 13. A manifold (1) as claimed in claim 1characterised in that each first port (35, 70) through which heattransfer medium is drawn from the flow heat transfer medium region (66)is provided with a means (78) for directing the heat transfer mediumbeing drawn from the flow heat transfer medium region (66) downwardlytowards the said first port (35, 70).
 14. A manifold (1) as claimed inclaim 1 characterised in that each second port (36, 73) for deliveringheat transfer medium into the return heat transfer medium region (67) isprovided with a means (79) for directing the heat transfer medium beingdelivered into the return heat transfer medium region (67) downwardlyinto the said region (67).
 15. A manifold (1) as claimed in claim 1characterised in that each second port (36, 73) through which heattransfer medium is drawn from the return heat transfer medium region(67) is provided with a means for directing the heat transfer mediumbeing drawn from the return heat transfer medium region (67) upwardlytowards the said second port (36, 73).
 16. A manifold (1) as claimed inclaim 1 characterised in that at least two pairs of first and secondports (35,36) are provided for connecting two circuits (6,7) each havingat least one heat exchanger for transferring heat from the heat transfermedium in the respective circuits (6,7).
 17. A manifold (1) as claimedin claim 1 characterised in that at least two pairs of first and secondports (35, 36, 70, 73) are provided for connecting two circuits (3,4,5)each having at least one heat source for heating the heat transfermedium.
 18. A manifold (1) as claimed in claim 1 characterised in thatthe container (20) comprises a top wall (21) and a bottom wall (22), thefirst and second ports (35, 36, 70, 73) being located in the top andbottom walls (21,22), the second ports (36) which are located in the topwall (21), communicating with the return heat transfer medium region(30) through the second connecting pipes (39), and the first ports (35,70) which are located in the bottom wall (22) communicating with theflow heat transfer medium region (29) through the first connecting pipes(37).
 19. A manifold (1) as claimed in claim 18 characterised in thatthe container (20) comprises a pair of spaced apart end walls (24)joining the top and bottom walls (21,22), respective first and secondports (35, 36, 70, 73) being located in end walls (24).
 20. A centralheating system as claimed in claim 19 characterised in that at least twocircuits (6,7) of the central heating system (2) comprise at least oneheat exchanger each for transferring heat from the heat transfer mediumin the respective circuits (6,7).